The invention relates to a method and a device for winding a running paper web to form a reel. The following prior art are relevant:
(1) DE 40 07 329 PA1 (2) DE 32 44 510 PA1 (3) FR 15 13 694 PA1 (4) GB 12 97 812 PA1 (5) U.S. Pat. No. 1,923,670 PA1 (6) EP 0 483 092 A1
Winding machines for winding paper webs are arranged either at the end of a papermaking machine, to wind the paper web accumulating there into a reel, or they are also used for rewinding a finished reel in order to produce reels with a quite specific winding quality.
In every case, the roll is intended to have quite specific properties, particularly related to the winding hardness. The winding hardness is intended to fall from a specific starting value to a final value, as a hard core winding is particularly important at the beginning. The decrease in hardness is intended to be as uniform as possible from the first to the last wound layer. The decrease is intended to have a specific gradient, that is to not be too severe or too weak. The profile of the winding hardness is intended in no case to have jump points, i.e., a sudden drop. No radial or tangential stresses should occur in the roll which might impair or destroy the paper web.
All this has previously been sought, but not achieved. Known winding machines instead produce, for example, rolls in which the core is either extremely soft or extremely hard and also in which there is a sharp drop in the winding hardness toward the end of the winding, at about four-fifths of the roll diameter. The first part, that is, the extremely soft or hard core, is unusable, specifically because the web suffers longitudinal compression in this region and splits. This part of the web has to be discarded as broke. In the final end region, in which the roll is not wound sufficiently hard, there is lateral displacement of the layers in relation to one another, so that the ends of the finished reel have a frayed appearance and the web edges can easily be damaged.
A poorly constructed core, with too low or too great a hardness, specifically does not allow satisfactory construction of the rest of the roll. The problem is particularly serious for pressure sensitive papers, for example, for self copying (NCR) papers. For these papers, close limits are placed on the pressing of the shell, with the roll being produced which is located on the shell, against the outer surface of the carrier drum.